Evaluation of the PrimeFlow RNA assay as a method of detection of SARS-CoV-2 single and dual Infections

Given the implications of increased transmissibility, virulence, host range, and immune escapes of emerging variants of SARS-CoV-2, developing in vitro models that allow for detection of variants and differences in infection dynamics is important. The objective of this study, was to evaluate the PrimeFlow RNA in-situ assay as a method of detection for multiple strains of SARS-CoV-2. Evaluation of detection and infection statuses included single infections with an Alpha, Delta, or Omicron variants and dual infections with Alpha/Omicron or Delta/Omicron. RNA probes specific for the Spike protein coding region, were designed (omicron or non-omicron specific). SARS-CoV-2 RNA was detected in greater frequency in the Vero E6 and minimally in the fetal deer testicle cell lines by flow cytometry using this approach for viral detection of multiple variants. Most evident in the Vero E6 cells, 24 h post infection both Alpha and Delta predominated over Omicron in dual infections. This is the first report using the PrimeFlow assay for the detection of SARS-CoV-2 at the single-cell level and as a potential model for competition of variants utilizing infection dynamics in cell culture.

A Mouse Model to Study the Pathogenesis of γ-herpesviral Infections in Germinal Center B Cells

CD30-positive germinal center (GC)-derived B cell lymphomas are frequently linked to Epstein-Barr Virus (EBV) infection. However, a suitable animal model for the investigation of the interplay between γ-herpesvirus and host cells in B cell pathogenesis is currently lacking. Here, we present a novel in vivo model enabling the analysis of genetically modified viruses in combination with genetically modified GC B cells. As a murine γ-herpesvirus, we used MHV-68 closely mirroring the biology of EBV. Our key finding was that Cre-mediated recombination can be successfully induced by an MHV-68 infection in GC B cells from Cγ1-Cre mice allowing for deletion or activation of loxP-flanked cellular genes. The implementation of PrimeFlow RNA assay for MHV-68 demonstrated the enrichment of MHV-68 in GC and isotype-switched B cells. As illustrations of virus and cellular modifications, we inserted the EBV gene LMP2A into the MHV-68 genome and induced constitutively active CD30-signaling in GC B cells through MHV-68 infections, respectively. While the LMP2A-expressing MHV-68 behaved similarly to wildtype MHV-68, virally induced constitutively active CD30-signaling in GC B cells led to the expansion of a pre-plasmablastic population. The findings underscore the potential of our novel tools to address crucial questions about the interaction between herpesviral infections and deregulated cellular gene-expression in future studies.